Transmission dynamometer



y 3 M. A. SMITH, JR- 2,049,330

TRANSMI S S ION DYNAMOMETER Filed Oct 27, 1951 2 Sheefs-Sheet 1 July 28, 1936. M. A. SMITH, JR

TRANSMISSION DYNAMOMETER 2 Sheets-Sheet 2 Filed Oct. 27, 1951 /A/ we N 7-041? M/ .Z, 4% M M. w

w th its as, 1936 .TEANSMSSION DYNOMETEB Marshall a. Smith, In, South Bend, nis.

Application oetobei- 2'1, 1931, semi No. 511,431

in the novel arrangement, construction, and asso-' 15 ciation of parts hereinafter more fully described and explained, with reference to the accompanying drawings, wherein:

Figure 1 is a diagrammatic view of a transmission dynamometer illustrating one application of go the invention;

Figure 2 is a cross section taken on line 2-2 of Figure 1.

Figure 3 is a diagrammatic view of 'a dynamometer embodying a modification of the inven- 25 tion, and

Figure 4 is a cross section on line H of Figure 3.

This transmission dynamometer consists of a driving member and a driven member. The driv- 30 ing member including a driving shaft I to which is keyed or otherwise rigidly fastened the hub portion 2 of the driving wheel, which hub portion is connected to the rim 3 of the wheel by spokes 4. The spokes 4 are machined integral '35 with the hub portion 2 and with the rim 3. Be-

tween each pair of spokes 6 is located a short spoke or stub arm 5. These stub arms 5 are also machined integral with the hub portion and have faces 6' parallel to the faces I of bosses 8 on the 4.0 spokes d. Carbon piles or other electrical resistance units, the resistances of whichare functions of the length or pressure on them are secured between the faces 6 and 1 and are insulated therefrom by insulating'members 9. These re- 45 sistance units, indicated at a and "b, may be arranged in such a manner as to be put under initial compression by adjusting screws.

In Fig. 1, the resistance units are shown connected in series, the terminals 10 and II of the 50 en units being connected with slip rings l2 and I3 which are insulated from the spokes 4 by the insulating blocks Id. The slip rings 12 and I3 are connected through brushes I5 and i8 and leads I! and it to any set of instruments, such 55 as'an ammeter l9 and a voltmeter 20, appropriate for measuring the resistance of the resistance units "a and b; The battery 2| supplies the electrical current necessary for the measurement of the resistance units.

, While a series connection of the resistance 6 units may be used, as shown in Fig. 1,'any seriesparallel, parallel, or differential connection may also be used. An advantageous connection of the resistance units is shown in Fig. 3. In this connection, all the resistance units a on the leading 10 sides of the spokes are connected in series, and all the resistance units b on the trailing sides of the spokes are connected in series. The two sets or-groups of resistance units are then connected through slip rings l2, l3, and 22, brushes 15 I5, i6 and 23, and leads i1, i8, and 24, to battery 21 and to two adjustable resistances Ri and R2 to form a Wheatstone bridge. Any unbalance in the resistance of the two sets of resistance units is then indicated by the deflectionoi. the pointer needle of the galvanometer G".

. r The driven member consists of a rim 25 conrigidly secured by bolts or other fasteners 29 to the rim 30f the driving member, the spokes 4 of which being resiliently flexible are deflected when the device is transmitting power. The deflection of the spokes is a function of the load 30 transmitted; therefore, the deflection of the spokes is measured by resistance elements.

In operation, when power is transmitted from the driving shaft through the dynamometer, the resisting torque of the driven shaft causes the spokes 6 of the driving member to tend to bend slightly as shown by the dotted line structure of Fig. 3. This slight bend relieves slightly the mechanical pressure on the resistance units a. on the leading sides of spokes 4 and increases slightly the mechanical pressure on the resistance units. 17" on the trailing sides of the spokes. The value of the resistance offeredby them decreases proportionately as they are compressed or shortened and increases proportionately as they are relieved of compression and permitted to expand. This decrease in pressure on one half of the resistance 'units and increase in pressure on the other half of the units causes an unbalance in the electrical currents flowing in the Wheatstone bridge, and 60 the galvanometer needle is deflected.

The junction between the hub 2 and each spoke 4 may be considered as the pivot point about which the spoke bends when transmitting power and due to the bending movement of the spokes,

of one group will always be less than the sum of the mechanical pressures on units is of the other group. Therefore, the difierence between the two resultant group pressures will have :a net mechanical pressure in favor of units "b. The net electrical resistance will, however, be in favor of units a and this net electrical resistance will be in proportion to torque. Since the electrical resistance of the units is a function of the pres-- sure acting upon them, and. since the electric current,which flows in the galvanometer of the Wheatstone bridge is a function of the diflerence in the electrical resistance of the twosets of resistance units, then the deflection of the galvanometer needle will be a function of the force acting upon the resistance units, and consequently of the torque transmitted through the dynamometer.

.It is obvious that if a series of readings is taken from the galvanometer corresponding to lmown [torques that this device can be used to indicate the torque transmitted throughthe dynamoni-' eter at any time. From the torque force and the revolutions per minute, the power transmitted may be computed.

Having thus described the invention, what 1 claim is:

1. A transmission dynamometer having, in combination, a driven member, a driving member having a plurality of radial spokes, alternate spokes being coupled with the driven member and being resiliently flexible to' be deflected by the resisting torque of the driven member when power is transmitted from the driving member, the remaining spokes being non-flexible, electrical resistor elements the resistance of which varies withpressure confined between the said radial spokes so that each resistance element is located between a spoke which may flex and-one which will not, said units electrically connected to provide two separate resistance groups, the resistance of one group of which is increased and the other decreased by the deflection, and means for indicating any unbalance in the resistance of the two groups.

'2. A transmission dynamometer comprising a driving member, a driven member, rigid elements on the driving member, deflectable elements cou= pling the said driving and driven members andtending to bend relative to the rigid elements in response to the resisting torque of the driven mem-,

- her and a driven member, a torque wheel consist,-

of a rim adapted to be coupled with one of the sum of the mechanical pressures on units a 3. A w meter having, in a combination, a driving shaft, a drivenv shaft, 5 driving and driven members fixed on the said driving and driven shafts respectively and hav- 8 rigidly coupled rims, the said driving member 5 having its rim connected with a .hub portion by deflectable spokes tending to bend in repsonse to the resisting torque of the driven member when power is transmitted from the driving member, rigid stub arms integral with the said hub portion and projecting radially thereof and between the said defiectable spokes, said spokes and stub arms having confronting parallel faces, and electrical means for transmitting and indicating torque including pressure-responsive resistances secured between confronting faces of the said spokes and stub arms.

4. A transmission dynamometer having, in combination, a driving shaft, a driven shaft, driving and driven'members fixed on said driving and driven shafts respectively, means for transmit-.- ting the motion of the driving member to the driven member, said driving member consisting of a hub having rigid stub arms'integral therewith and projecting radially therefrom and a rim tween a rigid stub arm and a deflectable spoke so as to be elongated or compressed in direct pro- 5 portion to the amount and direction of the occurring bending ofthe said spoke.

- 5. In a transmission dynamometer for deter- I mining the torque force between a driving memthe members, a hub adapted to be coupled to the other member and having a short rigid spoke and an elongated flexible spoke, said flexible spoke being connected with the rim and'being deflected from its normal position relative to the rigid spoke by the resisting torque of the driven member when the power of the driving member is transmitted thereto through the said wheel, an

elastic element connecting the rigid spoke and the flexible spoke and being elongated or compressed in proportion to the direction and extent of deflection of the flexible spoke, and means controlled by said elastic element for indicating at a distance the amount of the elongation or com- .pression of the elastic element.

MARSHALL A. SMITH, JR. 

